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MrSeb writes "Electrical engineers and material scientists at MIT have created a fiber-borne laser that could be woven to form a flexible display that could project different 3D images in any number of directions, to any number of viewers. MIT's fiber is similar to standard telecoms fiber, but it has a tiny droplet of fluid embedded in the core. When laser light hits the fluid, it scatters, effectively creating a 360-degree laser beam. The core is then surrounded by layers of liquid crystal, which can be controlled like 'pixels,' allowing the laser light to escape from specific points anywhere along the length of the fiber. This means that you could have a display that shows one picture on the 'front' and another on the 'back' — or different, glasses-free 3D images for everyone sitting in front and behind. In the short term, the laser fiber is more likely to have a significant application in photodynamic therapy, an area of medicine where drugs are activated using light. Photodynamic therapy is one of the only ways to treat cancer in a relatively non-invasive and non-toxic manner. MIT's laser could be threaded into almost any part of the body, where the ability to produce pixels of laser light at any point along its length would make it a highly accurate device."

It's still going to suffer the problem whereby your focal plane and triangulation point (Is there a word for where both eyes' 'beams' are pointing to? Sorry for the lame words.) are in the same place, despite the images logically appearing in front of and behind that plane as far as your brain can tell.

I reckon it's this disconnect between what you are seeing and what your eyes are doing that causes the headaches & strain.

If I understand this, the real possibility it enables is a true holographic display, not split images. The point is that one can deliver light with both amplitude and phase information to a fine-grained pixel grid. In principle, then, one can create outgoing waveforms of arbitrary shape, leading one to Casimir's prophetic statement (that I'm trying to recall, not look up): "If you see a lion in a cage, you cannot be certain that there really is a lion in the cage, as there could instead be a peculiar charge-current density that gives rise to the appearance of a lion". This is actually more formally stated as the Casimir Paradox -- because the solution to the EM field equations can be written as an integral equation with a surface (inhomogeneous) term, one can always reproduce the solution exterior to a closed subvolume produced by sources within that subvolume with a surface charge-current distribution that produces the same exterior solution.

The lasers themselves would then be the charge-current distributions. The interesting question would be how to modulate them with the requisite holographic encoding including phase information, at sufficient resolution to produce a clean 3D image.

That's usually called convergence [wikipedia.org]. It's one of at least 5 ways that humans infer distances and reconstruct the third dimension from what they see:
1. Focal depth: based on how much the eye's lens has to focus
2. Convergence: based on the slight differences in pointing of the two eyes
3. Stereoscopy: based on the slight differences between the left and right image
4. Parallax: the different displacements/motions of objects at different distances (e.g. when you move your head)
5. Visual inference: reconstructing using cues like occlusion, lighting, shadows, etc.

As long as all 5 of those don't agree, the image won't look 'truly 3D': it will seem wrong at in many cases can cause headaches or nausea (your brain is getting conflicting information for which there is no physically-correct solution). The reason that current 3D systems fail is that they don't match all 5. A regular 2D movie (or a photograph, etc.) gives you #5 and that's it. This works actually remarkably well. Glasses-based 3D systems try to trick you by giving each eye a slightly different image, which adds #3, but since 1,2 and 4 are still wrong, the overall effect feels weird: your eyes still have to point at, and focus on, the movie screen. (It's even worse for 3D-TV since you are focusing on something relatively close to you.)

The reason this happens is precisely because a movie/TV screen has spatial resolution (each pixel is different) but no angular resolution (the image on the screen is the same regardless of where your head/eyes are positioned). If you could add back in the angular information (with enough resolution), then you could create an arbitrary light field, that was indistinguishable from a physically-realistic light field. If done right in terms of angular resolution and computing a physically-correct light field, then this would give you 1,2, 3, and 4. (And 5 also, if what's being projected is a realistic scene with proper shadowing and so forth.) If the light field is properly created, each eye will get a slightly different image (since each eye is at a slightly different angle with respect to the screen); these images will change as you move your head around; and your eyes will in fact NOT focus or converge on the location of the screen: they will focus and converge on the virtual image being created by the light field emanating from the screen. (This is similar to a hologram, which can be a two-dimensional sheet and yet reconstruct the light field that would come from a three-dimensional object, and can create virtual images that are not in the plane of the sheet.)

The prototype being demonstrated in this article is not good enough to do that, mind you: they don't have enough angular resolution to trick your eyes. However that's where this technology is headed, and if it's done at high enough resolution, we will finally get proper 3D: where we're not just tricking your eyes, but where we're actually projecting the correct light field towards the viewer.

Well put. I think that you still get #2 and #4, though. The difference in the two pictures does affect the convergence. Your eyes try to line up the two images. They can, in fact, alter the convergence in editing to make things more exaggerated, which does cause plenty of headaches of its own. You get #4 by the camera's movement rather than head movement. Even if we could get #1, I don't think I'd want it. Focus pull is part of cinematography. If you can't force some things to be in focus and some th

You may lose one tool, but cinematography will adapt. There are tons of people who complained about how adding sound to movies would ruin things, and then later adding color, and then going digital. None of those things ruined movies. Things adapted. New techniques were created. The same things will happen with 3d.

I agree with KingMotley that cinematography will adapt, but I think the really exciting application would be communication. Imagine a wall-sized display using this display technology but where every tenth pixel is a lens feeding data into a light field camera [lytro.com]. You could virtually join your living room or office with someone's on the other side of the world (kinda like the floor to ceiling 3D display on the TNG Enterprise). Speaking as someone who lives far away from many of my loved ones, I think that would

If this is holographic (and why use lasers if it sn't?), it will certainly be awesome.

Your glasses-assisted 3D movies aren't really 3D. Your eyes' focus provides distance information to the brain, as does the stereoscopic rangefinding. When the rangefinder says the object is three feet away and the lenses are focused fifteen feet away, you're going to get muscle strain and headaches.

You don't have this with holograms. Holograms are true 3D. Shift your head a little when viewing a hologram and you can see ar

Easier to couple into the fiber. LED is a huge optical PITA to properly couple into a fiber. Yes LEDs are more mass produced and are cents instead of bucks but the coupling apparatus is bulky and "expensive" and generally a PITA, and by the time you spend a couple bucks on some fancy package and/or connector and focusing optics why not spend a buck on a bright laser instead of the dimness you'd get from a 10 cent LED? Now with superbright LEDs this argument is probably going away in the future, but not q

Lasers with cylindrically symmetric polarization states are predominantly based on whispering-gallery modes, characterized by high angular momentum and dominated by azimuthal emission. Here, a zero-angular-momentum laser with purely radial emission is demonstrated. An axially invariant, cylindrical photonic-bandgap fibre cavity8 filled with a microfluidic gain medium plug is axially pumped, resulting in a unique radiating field pattern characterized by cylindrical symmetry and a fixed polarization pointed in the azimuthal direction. Encircling the fibre core is an array of electrically contacted and independently addressable liquid-crystal microchannels embedded in the fibre cladding. These channels modulate the polarized wavefront emanating from the fibre core, leading to a laser with a dynamically controlled intensity distribution spanning the full azimuthal angular range. This new capability, implemented monolithically within a single fibre, presents opportunities ranging from flexible multidirectional displays to minimally invasive directed light delivery systems for medical applications.

In answer to your question, no this isn't a hologram, although in some sense it achieves a similar goal. Regular screens control the emission of light as a function of position. Holograms control not just the intensity of the emanating light but also the phase; this phase information carries all the extra information about the light field passing through a given plane. This new device controls the intensity and angular spread of the light coming from each pixel, which is also thereby controlling the full shape of the light-field being emitted from the plane of the screen.

With both a hologram and this directional-emission concept, you're controlling the angular spread of the light coming from each point, are thus fully specifying the light-field, and thus creating 'proper 3D' that is physically-realistic and fully convincing. (Assuming you have enough angular resolution in your output to create the small differences the eye is looking for, of course.)

As for why they are using a laser as the source light, it's mostly because they want detailed polarization control. (Coupling lasers into fiber-optics is well-established technology for telecommunications.) By controlling the exact mode of the laser-light propagation through the fiber, they can control the polarization of the light that shines out of the fiber, and thereby use conventional tricks to modulate that light. In particular, in an LCD screen, small fields are used to re-orient liquid-crystal molecules, which then either extinguish or transmit the light (based on whether the orientation of the LC molecule is aligned with the polarization of the light).

Overall it's an ingenious trick: have a light fiber emit light with controlled polarization. Then have a series of LC pixels on the outside of the fiber, whose orientation can now not just modulate the intensity of emission as a function of position along the fiber, but also as a function of angle for each position along the fiber. The end result is that you control the light field emanating from the device, and so can (in principle) reconstruct whatever full-3D image you want.

Of course the prototype in the article only has four LC channels along the fiber. Enough to create a different image on the front vs. the back of the screen. Not nearly enough to create realistic 3D. Also they are only controlling the angle in one direction (around the fiber axis), a

The data and bandwidth requirements might then be several orders of magnitude higher than for current 3D displays. I suppose, though, that that is a given, and we'll cross that bridge when we get there, as we usually do.

The holograms I worked with in college used film (late 1970s), and the holograms had a bit of grainines to them, so we're probably going to need a hell of a lot better displays before we get hologram displays.

The problem with headaches at least for me, is if I am trying to look around and see all the other details and my eyes are moving around and the objects 3d perspective doesn't change correctly. Or they make the 3d off slightly so it is too 3d for my eyes thus making me try to focus on the wrong part of the movie

If you get a headache it is usually because you are looking at stuff that the producer doesn't want you to see it.

is a 360 degree laser beam?
Laser light is coherent light travelling in one direction, and this light spreads out in all directions... so what exactly makes this be laser light, once it leaves the fiber? I think the correct technical term would just be "light."

There are some lasers which are not single spatial mode and consequently their light beams diverge more than required by the diffraction limit. However all such devices are classified as "lasers" based on their method of producing that light: stimulated emission. Lasers are employed in applications where light of the required spatial or temporal coherence could not be produced using simpler technologies.

The light originally came from a laser, so it's laser light even though its diverging in all directions. Bollocks.

In addition to the laser device being the source of the light, I believe that the highly monochromatic nature of the light is part of the 'laser light' essence. This is presumably preserved regardless of the spatial dispersion.

Laser light is coherent (which has to do with waveform). That's its fundamental property. The fact that it comes out of most lasers already collimated to a great extent is just a bonus side-effect of the way those lasers are built.

Laser light is coherent (which has to do with waveform). That's its fundamental property. The fact that it comes out of most lasers already collimated to a great extent is just a bonus side-effect of the way those lasers are built.

But most lasers are only coherent for a distance of millimeters or less and they are used for their brightness and/or narrow bandwidth. They are useless for holography and interferometry.

The light originally came from a laser, so it's laser light even though its diverging in all directions. Bollocks.

LASER means Light Amplification by Stimulated Emission of Radiation, nothing more. If you want to have a word for the properties of the light rather than the means of generation you should probably find another word.

There IS a word. Coherent. The fact that lasers are generally for the creation and use as coherent light sources is the cause of the confusion.

If you want to be pedantic, laser light is light produced by amplification based on stimulated emission. The light tends to be temporally coherent (in-phase) and spatially coherent (single point), but neither is necessary. If they've managed to spread out a laser beam while keeping it in-phase and polarized, it's very much laser light, just not focused.

I know there is a lot going on in this article that is technically over my head, but I wish people would stop talking about "glasses free" 3D like it's some futuristic flying car. The 3DS has been out for a year, and it has 3D tech for game playing, photo taking and video recording in a $170 kids toy. I know there are a couple of cell phones also. I'm sure the fiber optic stuff is great and all, but glasses free 3D is here now.

While I agree there should be a distinction made (just as I detest the term 3D for stereoscopic image) this tech is entirely different than the 3DS.

This would theoretically allow for a movie theatre full of people to each be broadcast their own version of the movie with the correct perspective point thereby making stereoscopic *almost* worthy of the 3D moniker.

So while it should be called "multi-perspective glasses-free stereoscopic display" the simple fact is you're rant is completely unwarranted, the tech

And, I suppose you are going to say your laser can be used to cure cancer now.

MIT's laser could be threaded into almost any part of the body, where the ability to produce pixels of laser light at any point along its length would make it a highly accurate device."

You didn't disappoint. Unfortunately your entertaining article is rather short. If it was a bit longer, I would have expected solutions for rebuilding the glacier shelf and ending violence in the mid-east.

Seems like this would have big potential for use in all-optical routing, but I did not see any mention of that in the articles. Any optical routing pros out there who can tell us if this tech is applicable?